Heat sink with heat bus and fin structure

ABSTRACT

A heat sink to remove heat from a processor within a chassis to air moving through a fin structure on the heat sink. An embodiment of the heat sink comprises a heat bus engaging the processor to conduct heat from the processor to a fin structure having interconnected, repeating cellular air channels. A U-shaped heat bus comprises a base and first and second legs extending therefrom connected to opposite sides of the fin structure. An embodiment of the heat bus has a solid conductive core to conductively transfer heat from the processor through the base and the first and second legs to sides of the fin structure. Alternately, an embodiment of the heat bus has a hollow core containing a fluid to evaporatively transfer heat from the processor through the base and the first and second legs to sides of the fin structure.

BACKGROUND

1. Field of the Invention

The present invention relates to heat sinks to remove heat fromheat-generating electronic devices, such as computer processors.

2. Background of the Related Art

Computer systems often rely on heat sinks positioned on heat-generatingelectronic components, such as processors, to maintain performance ofthe component by removing heat and thereby maintaining a favorableoperating temperature. Heat sinks generally conduct heat generated by acomponent to fins where the heat is transferred into an air flow acrossthe surface area of the fins. Heat sinks are available with severaltypes of air-cooled fins including pin fins, straight fins, folded fins,flared fins and extruded fins. With increasing processor powerdensities, more heat is generated by processors disposed within thelimited space of the computer chassis. It is important that the heatsink is sufficient to maintain the performance of the processor andstill fit with the space and form factor of the chassis.

Heat sink fin structures with larger surface areas for convective heattransfer are able to dissipate more heat to surrounding air, but merelyincreasing the size and number of fins yields diminishing returns forthe space consumed. Dense electronic configurations and increasingprocessor power densities demand greater heat-dissipation capability tomaintain processor performance while controlling heat sink cost andweight.

BRIEF SUMMARY

One embodiment of the present invention provides a heat sink comprisinga fin structure having a plurality of repeating, interconnected fincells that allow the movement of air through the fin cells, wherein thefin structure further includes a first side and a second side. The heatsink further comprises a heat bus that thermally engages aheat-generating electronic component and the first side and the secondside of the fin structure, wherein the heat bus facilitates the transferof heat from the heat-generating electronic component to the first andsecond sides of the fin structure, and wherein the fin structure haslateral conductive pathways to conduct heat from the first and secondsides of the fin structure toward a central region of the fin structure.

Another embodiment of the invention provides a heat sink comprising afin structure having a plurality of interconnected repeating cellularair channels that allow the movement of air there through to remove heatfrom the fin structure. The heat sink further comprises a heat bushaving a first portion conductively connected to a bottom of the finstructure, a second portion conductively connected to a first side ofthe fin structure and a third portion conductively connected to a secondside of the fin structure, wherein the heat bus facilitates the removalof heat from the first portion of the heat bus to the first side andsecond side of the fin structure for dissipation to air moving throughthe air channels of the fin structure.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of a heat sink of thepresent invention comprising a heat bus connected to a honeycomb finstructure having a plurality of interconnected, repeating cellular airchannels.

FIG. 2 is a section end view of an embodiment of a heat sink of thepresent invention comprising a honeycomb fin structure coupled to aU-shaped heat bus.

FIG. 3 is a section end view of a second embodiment of a heat sink ofthe present invention comprising a honeycomb fin structure coupled to aU-shaped heat bus having a portion that conforms to the side of the finstructure.

FIG. 4 is a perspective view of a third embodiment of a heat sink of thepresent invention comprising a honeycomb fin structure coupled to aU-shaped heat bus having a plurality of branches to enhance heatdistribution to the fin structure.

FIG. 5A is a perspective view of a fourth embodiment of a heat sink ofthe present invention comprising a honeycomb fin structure coupled to aU-shaped heat bus having a broad profile to enhance heat distribution tothe fin structure.

FIG. 5B is a perspective view of a modified fourth embodiment of theheat sink of FIG. 5A comprising a honeycomb fin structure coupled to aU-shaped heat bus that extends the length of the honeycomb fin structureto further enhance heat distribution to the fin structure.

FIG. 6 is a section end view of an embodiment of a heat sink of thepresent invention comprising a honeycomb fin structure coupled to aU-shaped heat bus that comprises a U-shaped heat pipe.

FIG. 7A is a section end view of another embodiment of a heat sink ofthe present invention comprising a honeycomb fin structure coupled to aheat bus that substantially surrounds the fin structure and comprisestwo heat pipes.

FIG. 7B is a perspective view of an embodiment of a heat sink comprisinga honeycomb fin structure coupled to a heat bus that substantiallysurrounds the fin structure.

DETAILED DESCRIPTION

Embodiments of the heat sink of the present invention comprise a heatbus and a fin structure to remove heat from a heat-generating electroniccomponent, such as a processor. An embodiment of the heat sink of thepresent invention comprises a fin structure for dissipating heat to airflowing through air channels within the fin structure. The fin structurecomprises repeating interconnected cellular air channels that may becircular or have a plurality of sides and shapes. Examples of suchrepeating interconnected cellular air channels include hexagonal(honeycomb) air channels, pentagonal air channels, quadrilateral (e.g.,trapezoidal, rectangular or square) air channels and triangular airchannels, or combinations of two or more of these. The fin structuregenerally comprises a bottom intermediate, a first side and a secondside.

An embodiment of the heat sink of the present invention furthercomprises a heat bus to move heat from one or more hot locations to oneor more cold locations, the heat bus having a first portion at a hotlocation and one or more second portions conductively connected to a finstructure at cold locations. The one or more second portions may, forexample, be connected to the fin structure at the bottom, at the firstside and/or at the second side of the fin structure.

The heat bus may, in one embodiment, comprise two or more branches toprovide more than one heat conduit through which heat may move from thebase to the fin structure. In a heat bus with two or more branches, heatmay move from a base of the heat bus that engages the processor to aright branch of the heat bus that is connected to a right portion of thebottom of the fin structure and to a right portion of the fin structureadjacent to the right portion of the bottom of the fin structure, andheat may also move from the base of the heat bus to a left branch of theheat bus that is connected to a left portion of the bottom of the finstructure and to a left portion of the fin structure adjacent to theleft portion of the bottom of the fin structure. Multiple branches ofthe heat bus provide increased heat transfer capacity to move heat fromthe base through the heat bus to the fin structure for dissipation toair flowing through air channels within the fin structure.

In one embodiment, the heat bus is further connected to a top of the finstructure. For example, an embodiment of a heat sink may have a heat buscomprising a right leg conductively connected to a right portion of thebottom of the fin structure, to a right portion of the fin structureadjacent to the right portion of the bottom of the fin structure, and toa right portion of the top of the fin structure adjacent the rightportion of the fin structure. The heat bus may further comprise a leftleg connected to a left portion of the bottom of the fin structure, to aleft portion of the fin structure adjacent to the left portion of thebottom of the fin structure, and to a left portion of the top of the finstructure adjacent the left portion of the fin structure. In thisconfiguration, the heat bus provides increased capacity to move heatfrom the base to substantially the entire periphery of the finstructure, vertically from the base and the top of the heat bus to acentral region of the fin structure and laterally from the right portionand the left portion to the central region of the fin structure for moreuniform dissipation of heat to air flowing through the fin structure.

A “heat bus,” as that term is used herein, is a heat conduit to transferheat from a hot location at a base to at least one cold location at aportion of a fin structure remote from the base. A heat bus may comprisea spreader bar, which may be an elongate and/or branched heat conduithaving a generally solid core to conduct heat from a hot location to atleast one cold location, and the spreader bar may comprise a highlythermally conductive material such as copper. A heat bus may comprisetwo or more legs or branches to enhance heat distribution to a finstructure, and the legs or branches of the heat bus may comprise two ormore legs or branches disposed, along with a base, in a U-shapedconfiguration to increase heat conduction from a hot location at thebase to one or more cold locations on the fin structure.

A heat bus may comprise a heat pipe, a conductive member having a hollowsealed core containing a fluid to transfer heat from a hot location toone or more cold locations by conduction, through the solid portion, andthrough cyclic evaporation and condensation of the fluid sealed withinthe hollow core. A wick member may be disposed within the hollow core topromote movement of the fluid along the hollow core of the heat pipe.The wick, which may, for example, comprise a few layers of a fine gauze,may be affixed to the inside surface of the core, and capillary forceswithin the wick will move condensate condensed from vapor at the“condenser” portion(s) at the cold location(s) of the heat bus to the“evaporator” portion(s) at the hot location(s) of the heat bus. If theevaporator portions(s) of the heat bus are lower in elevation than thecondenser portion(s), gravitational forces assist the capillary forceswithin the wick. A wickless heat pipe relies on gravitational forcesalone to move condensed fluid within the core from the condenserportion(s) to the evaporator portion(s) of the heat bus.

The improved distribution of heat from the base to the fin structureimproves cooling performance of the heat sink. The heat bus may alsodecrease the weight of the heat sink for a given heat dissipationcapacity and may thereby reduce the overall cost of the heat sink andthe computer in which the heat sink is installed.

FIG. 1 is a perspective view of an embodiment of a heat sink 10 of thepresent invention comprising a honeycomb fin structure 12 having an airinlet end 24 and an air outlet end 25 and a plurality of interconnected,repeating cellular air channels 15 for convection heat transfer from thefin structure 12 to air drawn through the air channels 15 by an airmover (not shown) that may be disposed in a computer chassis (not shown)in which the heat sink 10 is also disposed. The heat sink 10 furthercomprises a U-shaped heat bus 14 having a first leg 21 along a firstside of the fin structure 12, a second leg 23 (partially shown) along asecond side of the fin structure 12 and a base portion 26 there between.In the embodiment of FIG. 1, the base 26 is as wide as the width 27 ofthe fin structure 12. The base 26 of the U-shaped heat bus 14 of theheat sink 10 is adapted to thermally engage a processor (not shown)along a first face 28 to conduct heat from the processor to the finstructure 12 for convective heat transfer to air moving through the airchannels 15. The heat bus 14 conductively engages a bottom portion ofthe fin structure 12 along a second face 29 of the base portion 26 andis connected to the sides of the fin structure 12 at the first leg 21and the second leg 23. It will be understood that the interconnected,repeating cellular air channels 15 within the fin structure 10 providefor conduction of heat from the base 26 of the heat bus 14 and from thefirst leg 21 and second leg 23 of the heat bus 14 generally inwardlytowards the central region 50 of the fin structure 10. As used herein,the central region of the fin structure is generally defined by theintersection of a vertical axis of symmetry 49 and a horizontal axis ofsymmetry 60 of the fin structure 10.

FIG. 2 is a section end view of the embodiment of the heat sink 10 ofFIG. 1 with the heat sink secured over a processor 20. FIG. 2illustrates the honeycomb fin structure 12 coupled to a U-shaped heatbus 14 having a first leg 21 and a second leg 23 disposed along opposingsides 16 of the fin structure 12 of the heat sink 10. A thermalinterface material 22 is disposed intermediate the processor 20 and thefirst face 28 of the base 26 of the heat sink 10 to conform to the firstface 28 of the base 26 of the heat sink 10 and to a face 69 of theprocessor 20 and promote heat transfer from the processor 20 to the heatsink 10. The fin structure 10 of FIG. 2 comprises repeating andinterconnected hexagonal cells 13 that form elongate air channels 15extending from and into the sheet. Other embodiments of the heat sink 10may have fin structures 12 having alternative repeating andinterconnected cells 13, such as pentagonal cells, quadrilateral cells,trapezoidal cells, triangular cells or circular cells, and the structureof the heat sink 10 of the present invention is limited only by theclaims that are appended hereto.

The fin structure 12 of the embodiment of the heat sink 10 of FIG. 2comprises a plurality of landings 19 disposed along the sides 16 of thefin structure 12. The first leg 21 of the U-shaped heat bus 14 of FIG. 2is connected to the fin structure 12 at landings 19 by connections 18and the second leg 23 of the heat bus 14 is connected to the finstructure 12 by connections 18 at landings 19. Embodiments of the heatsink 10 of the present invention may include connections 18 that are,for example, welded, soldered, or brazed to enhance conductive heattransfer from the heat bus 14 across the connections 18 to the finstructure 12.

FIG. 3 is a section end view of alternate second embodiment of a heatsink 10 of the present invention, where the heat sink is secured overthe processor 20. The heat sink 10 comprises a honeycomb fin structure12 coupled to a U-shaped heat bus 14 having a first leg 21 having afirst side 15 and a second side 11 that generally conforms to the side16 of the fin structure 12 disposed adjacent to the first leg 21. TheU-shaped heat bus 14 further comprises a second leg 23 having a firstside 15 and a second side 11 that generally conforms to the side 16 ofthe fin structure 12 adjacent to the second leg 23. The second sides 11of the first leg 21 and the second leg 23 of the embodiment of theU-shaped heat bus 14 of FIG. 3 are in generally uninterrupted contactwith the sides 16 of the fin structure 12, and perhaps generallycontinuously connected to the sides 16, to enhance conductive heattransfer from the first leg 21 and the second leg 23 of the U-shapedheat bus 14 to the fin structure 12.

FIG. 4 is a perspective view of a third embodiment of a heat sink 10 ofthe present invention comprising a honeycomb fin structure 12 coupled toa U-shaped heat bus 14 having a base 26, a plurality of first legs 21and a plurality of second legs 23 (partially shown) along the opposingside of the fin structure. The first legs 21 and the second legs 23 areconnected to the landings 19 on the sides 16 of the fin structure 12 byconnections 18 to further enhance distribution of heat from theprocessor (not shown), through the base 26 and the first legs 21 andsecond legs 23 of the heat bus 14 to the fin structure 12. The firstlegs 21 are illustrated in FIG. 4 as being parallel and generallyequally spaced along the length of the fin structure 12 between theinlet end 24 and the outlet end 25 of the air channels 15 therein.

FIG. 5A is a perspective view of a fourth embodiment of a heat sink 10of the present invention comprising a honeycomb fin structure 12 coupledto a U-shaped heat bus 14 having a base 26, a first leg 21 having awidth 48 and a second leg 23 (partially shown) extending from the base26 and connected to landings 19 on the fin structure 12 by connections18. The first leg 21 and the second leg 23 of the heat bus 14 shown inFIG. 5A have a broad profile or width 48 to further enhance distributionof heat from the processor (not shown), through the base 26 and thefirst leg 21 and second leg 23 of the heat bus 14 to the fin structure12. It will be understood that other embodiments of the heat sink 10 maycomprise a heat bus 14 having a first leg and a second leg that are aswide (dimension 48) as the fin structure 10 is long from the inlet end24 to the outlet end 25.

FIG. 5B is a perspective view of a modified fourth embodiment of theheat sink 10 of FIG. 5A comprising a honeycomb fin structure 12 coupledto a U-shaped heat bus 14 having a first leg 21 and a second leg 23.Both legs 21, 23 have a length 47 that co-extends the entire length(from the inlet end 24 to the outlet end 25) of the honeycomb finstructure 12 to which the heat bus 14 is coupled further enhance heatdistribution to the fin structure 12.

FIG. 6 is a section end view of a fifth embodiment of a heat sink 10 ofthe present invention comprising a honeycomb fin structure 12 coupled toa U-shaped heat bus 14 that comprises a first L-shaped heat pipe 32 anda second L-shaped heat pipe 33. The first and second L-shaped heat pipes32, 33 comprise hollow cores 39 containing a fluid (not shown) such aswater that moves heat from hot locations 40 to cold locations 41 throughthe evaporation-condensation cycle. The first L-shaped heat pipe 32comprises a first portion 34 disposed within the base 26 of the heat bus14 and a second portion 35 disposed within a first leg 21 of the heatbus 14. Similarly, the second L-shaped heat pipe 33 comprises a firstportion 36 disposed within the base 26 and a second portion 37 disposedwithin the second leg 23. The base 26 receives heat by conduction fromthe processor 20 through the thermal interface material 22. Heat ismoved from the base 26 to both the first leg 21 and the second leg 23 byconduction through the solid portions 38 of the first leg 21 and thesecond leg 23 and by evaporation-condensation within the cores 39 of thefirst and second L-shaped heat pipes 32, 33. Air flow through the airchannels 15 removes heat from the fin structure 12 by convection.

FIG. 7A is a section end view of a sixth embodiment of a heat sink 10 ofthe present invention comprising a honeycomb fin structure 12 coupled toa heat bus 14 that substantially surrounds the fin structure 12. Theembodiment of the heat sink 10 of FIG. 7A comprises two U-shaped heatpipes 32, 33, each one open towards the other, to generally surround thefin structure 12. The first and second U-shaped heat pipes 32, 33comprise hollow cores 39 containing a fluid (not shown) that moves heatfrom hot locations 40 to cold locations 41 through theevaporation-condensation cycle. The first U-shaped heat pipe 32comprises a first portion 34 disposed within the base 26 of the heat bus14, a second portion 35 disposed within a first leg 21 of the heat bus14, and a third portion 42 disposed within a top 44 of the heat bus 14.The second U-shaped heat pipe 33 comprises a first portion 36 disposedwithin the base 26, a second portion 37 disposed within the second leg23 of the heat bus 14 and a third portion 43 disposed within the top 44of the heat bus 14. The base 26 receives heat by conduction from theprocessor 20 through the thermal interface material 22. Heat is movedfrom the base 26 to the first leg 21 and the second leg 23 by conductionthrough the solid portions 38 of the first leg 21 and the second leg 23and by evaporation-condensation within the cores 39 of the first andsecond U-shaped heat pipes 32, 33.

FIG. 7B is a perspective view of the an embodiment of a heat sink 10comprising a honeycomb fin structure 12 coupled to a heat bus 14 thatsubstantially surrounds the fin structure 12. The heat bus 14 of FIG. 7Bcomprises a heat spreader 59 having a first leg 21 that terminates atterminus 56 and a second leg 23 that terminates at a terminus 57. Thefirst leg 21 comprises a first portion 58 and a second portion 51. Thesecond leg 23 comprises a first portion 52, a second portion 53 and athird portion 54 extending across a top 55 of the fin structure 12 toterminus 57 of the second leg 23 at a position proximate to the terminus56 of the first leg 21 to provide a heat bus 14 that substantiallysurrounds the fin structure 12 to enhance heat distribution to the finstructure 12.

It should be understood that the heat bus 14 of FIG. 7A need not belimited to the two heat pipes 32, 33 and may be, in other embodiments ofthe present invention, multiple heat pipes or a single extended heatpipe. An embodiment of a heat bus 14 having a single extended heat pipemay comprise a heat pipe having a hollow core 39 that forms a continuousloop that surrounds the fin structure 12. It will be further understoodthat the heat bus 14 of the heat sink 10 of FIG. 7A will function as aheat spreader if the fluid within the cores 39 is omitted, therebyleaving the heat bus 14 to transfer heat by conduction only. It will befurther understood that the heat bus 14 of FIG. 6 would function if abase divider 46 in FIG. 6 that isolates the cores 39 within the firstand second legs 21, 23 one from the other is removed to place the cores39 in fluid communication one with the other, and that the heat bus 14of FIG. 7A would similarly function if the base divider 46 and the topdivider 45 in FIG. 7A that isolate the cores 39 within the first andsecond legs 21, 23 is removed to place the cores 39 in fluidcommunication one with the other.

It should also be understood that the heat bus 14 of FIG. 7B could, inanother embodiment of the present invention, comprise a hollowfluid-containing core to provide for heat transfer through anevaporation-condensation cycle within the hollow core and for heattransfer through conduction within the solid outer portion of the heatbus 14. It will be further understood that the first leg 21 and thesecond leg 23 could, in another embodiment, be made continuous andwithout terminus 56 of the first leg 21 and terminus 57 of the secondleg 23 so that heat bus 14 would form a generally continuous conductivestructure surrounding the fin structure 12. Still further, any terminus56, 57 could be centered along the top or otherwise positioned forconvenience of efficiency.

The term “repeating,” as that term is used in connection with “repeatinginterconnected cells,” does not imply any uniformity of shape or sizeamong the cells within the fin structure. To the contrary, as can beseen in FIGS. 1-7B, there are cells (for example, around the interiorregions of the cell structure) that appear as regular hexagons, cellsthat appear as isosceles triangles (near the top and bottom of the finstructure) and cells that appear as trapezoids (along the sides of thefin structure). It is not required that all air channels are identicalin cross-section or that all air channels are uniform along theirlength.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,components and/or groups, but do not preclude the presence or additionof one or more other features, integers, steps, operations, elements,components, and/or groups thereof. The terms “preferably,” “preferred,”“prefer,” “optionally,” “may,” and similar terms are used to indicatethat an item, condition or step being referred to is an optional (notrequired) feature of the invention.

The corresponding structures, materials, acts, and equivalents of allmeans or steps plus function elements in the claims below are intendedto include any structure, material, or act for performing the functionin combination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but it is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

What is claimed is:
 1. A heat sink, comprising: a fin structure having aplurality of repeating, interconnected fin cells allowing the movementof air through the fin cells, the fin structure further having a bottom,a first side and a second side; and a heat bus having a base tothermally engage a heat-generating electronic component, wherein theheat bus conductively engages and traverses at least a portion of thebottom of the fin structure, at least a portion of the first side of thefin structure, and at least a portion of the second side of the finstructure; wherein the heat bus facilitates the transfer of heat fromthe base to the first and second sides of the fin structure; and whereinthe fin structure has lateral conductive pathways to conduct heat fromthe sides of the fin structure toward a central region of the finstructure.
 2. The heat sink of claim 1, wherein the heat bus is a heatspreader with a solid conductive core.
 3. The heat sink of claim 1,wherein the heat bus is a heat pipe having a conductive outer portionand a sealed hollow core containing a fluid.
 4. The heat sink of claim1, wherein the fin structure further comprises a top.
 5. The heat sinkof claim 4, wherein the heat bus engages and traverses at least aportion of the top of the fin structure.
 6. The heat sink of claim 1,wherein the heat bus has a U-shaped cross-section.
 7. The heat sink ofclaim 6, wherein the heat bus comprises a U-shaped heat pipe.
 8. Theheat sink of claim 1, wherein the heat bus comprises a plurality ofbranches that conductively engage the first side of the fin structureand a plurality of branches that conductively engage the second side ofthe fin structure.
 9. The heat sink of claim 1, wherein theinterconnected repeating cells comprise hexagonal cells through whichair may pass to cool the fin structure.
 10. A heat sink, comprising: afin structure having a plurality of interconnected repeating cellularair channels allowing the movement of air there through to remove heatfrom the fin structure; and a heat bus having a first portionconductively connected to a bottom of the fin structure, a secondportion conductively connected to a first side of the fin structure anda third portion conductively connected to a second side of the finstructure; wherein the heat bus facilitates the removal of heat from thebase to the first side and second side of the fin structure fordissipation to air moving through the air channels of the fin structure.11. The heat sink of claim 10, wherein the heat bus is a heat spreaderwith a solid conductive core.
 12. The heat sink of claim 10, wherein theheat bus is a heat pipe having a conductive outer portion and a sealedhollow core containing a fluid.
 13. The heat sink of claim 10, whereinthe heat bus has a fourth portion conductively connected to the top ofthe fin structure.
 14. The heat sink of claim 10, wherein the heat bushas a U-shaped cross-section.
 15. The heat sink of claim 14, wherein theheat bus comprises a U-shaped heat pipe.
 16. The heat sink of claim 10,wherein the heat bus comprises a plurality of branches that conductivelyengage the first side of the fin structure and a plurality of branchesthat conductively engage the second side of the fin structure.
 17. Theheat sink of claim 10, wherein the interconnected repeating cellscomprise hexagonal cells through which air may pass to cool the finstructure.